"But it's not for me to speak any further on that matter."
Michael Clarke was upbeat Haddin would return at some point during the five-Test series.
"He's doing as well as he can do," Clarke said.
"It is pretty important we respect the privacy of the Haddin family and give him this chance to be with his family.
"I'm really confident that we'll see more of Brad Haddin throughout this series and he will play a big part in the rest of this series."
England captain Alastair Cook said his side's thoughts were with Haddin.
"I don't know the specifics, but when you hear it's for personal reasons you just hope his family are OK," Cook said.
It's understood Australia have made two changes as they seek to square the series 1-1, having been crushed by 169 runs inside four days at Cardiff.
Shane Watson has been replaced by fellow allrounder Mitch Marsh, who clubbed eye-catching centuries against Kent and Essex prior to the first Test.
Adam Voges is expected to field at first slip in place of Watson, whose reliability in the cordon never wavered during his slump with the bat.
Striking up an immediate understanding with Voges and mastering the unique Lord's slope that perplexes some keepers are two of Nevill's big challenges this week.
"Like any foreign conditions, there're unique challenges," Nevill said.
"It's special just being here. It's a tremendous ground.
"It is a tremendous honour and privilege to play for your country."
Nevill is making his Test debut at age 29, one year younger than Haddin.
His father in the middle of a last-minute dash across the world to watch day one of the second Test.
Nevill has tried to keep things as normal as possible, despite plenty of well-wishers contacting him on Tuesday and Wednesday.
"I didn't really have much time to think. I was too busy trying to throw my phone in the toilet - the thing wouldn't stop buzzing," he said.
- AAP
